1. Technical Field of the Invention
The present invention relates to a condenser, a power plant and an operation method thereof.
2. Description of Prior Arts
In a fossil power plant, nuclear power plant, or the like, steam exhausted from a steam turbine is cooled by a condenser using sea water as cooling water. However, since sea water is used as cooling water in the condenser as mentioned above, sea water has become a cause of corrosion or the like of structural apparatus and piping, etc. of the power plant when the sea water flowed into the condenser, so that it is necessary to monitor always water quality inside the system to find whether or not sea water leaks into the interior of the condenser. If the water quality inside the system exceeds a set value because of leakage of sea water into the interior of the condenser, a signal is issued from a detection part, and an alarm is generated on a monitor, operation panel, etc. An operator has received the alarm, identified a position and degree of the leakage, and judged whether or not the plant operation was stopped or continued according to the result, and they were operated manually.
Further, as an example of conventional water quality monitors, there are proposals disclosed in JP A 3-248030, JP A 6-11406 and JP A 5-264393.
For example, JP A 3-248030 discloses an apparatus in which a condenser hot well is divided into a first water chamber and a second water chamber by a partition wall, an electric conductivity measuring apparatus is provided in each water chamber and it is monitored whether or not an absolute value of difference between two electric conductivities is within an upper limit value. JP A 6-11406 discloses an apparatus in which the conductivity of a sample liquid which is taken from a condenser and deaerated by a gas-permeable film and the conductivity of a sample liquid taken from a recirculating water delivered by a condenser pump and deaerated in the similar manner are compared, whereby mixing of sea water is judged. Further, JP A 5-264393 discloses an apparatus in which water quality is detected in a plurality of positions of piping of a condenser system, leakage is judged at each position and total diagnosis of those leakage conditions are classified in steps and displayed.
However, the apparatus disclosed in JP A 3-248030, JP A 6-11406 and JP A 5-264393 each are provided with a detection point for taking out detection water in a condenser outlet through which the whole condensate passes, on the downstream side of a condenser pump for delivering condensate in the condenser, or in piping connecting from the condenser to a steam generator. However, in the case where the detection point is provided in the condenser outlet or on the downstream side of the condenser pump for delivering condensate in the condenser, or in the piping connecting the condenser to the steam generator, a time is taken until sea water leakage is detected, whereby there is the possibility that the water mixed with sea water is flowed out from the condenser even if the plant is stopped or a feed water system is closed after the detection of sea water leakage, and that the sea water-mixed water flows into the steam generator and steam turbine since the sea water-mixed water is delivered by the condenser pump.